// app.js
const fp = require('lodash/fp')
const { Maybe, Container } = require('./support')

//练习1：使用fp.add(x, y)和fp.map(f, x)创建一个能让functor里的值增加的函数ex1
let maybe = Maybe.of([5, 6, 1])
let ex1 = (x) => {
  //EX1
  return fp.map(fp.add(x))
}
//EX1 Test
console.log(maybe.map(ex1(3))._value)

//练习2：实现一个函数ex2，能够使用fp.first获取列表的第一个元素
let xs = Container.of(['do', 'ray', 'me', 'fa', 'so', 'la', 'ti', 'do'])
let ex2 = (xs) => {
  //EX2
  return xs.map(fp.first)._value
}
//EX2 Test
console.log(ex2(xs))

//练习3：实现一个函数ex3，使用safeProp和fp.first找到user的名字的首字母
let safeProp = fp.curry(function (x, o) {
  return Maybe.of(o[x])
})
let user = { id: 2, name: 'Albert' }
let ex3 = x => {
  //EX3
  return safeProp('name')(x).map(fp.first)._value
}
//EX3 Test
console.log(ex3(user))

//练习4：使用Maybe重写ex4，不要有if语句
let ex4 = function (n) {
  if (n) {
    return parseInt(n)
  }
}
//EX4
let ex42 = n => {
  return Maybe.of(n).map(parseInt)._value
}
//EX4 Test
console.log(ex4('1'))
console.log(ex42('1'))
console.log(ex4('2.2'))
console.log(ex42('2.2'))